Dental restorations or prostheses are often made of two or more components, with the individual components providing different characteristics for the restoration. For example, a framework may provide for good structural support, and a veneer may provide for good aesthetics. The framework generally is a supporting structure for the dental restoration that provides mechanical stability and usually comprises an interface by which the restoration can be affixed to a prepared tooth of a patient. The veneer provides for pleasing aesthetic characteristics so that the restoration resembles a natural tooth in shape and appearance. In addition, both the framework and the veneer are shaped to fit well with the adjacent and opposed teeth in a patient's mouth.
In recent years ceramic materials have been widely used for making high-quality dental restorations because of their good physical, aesthetic and biological properties. In some applications such dental restorations are made by combining a ceramic framework and a glass or glass ceramic veneer. The framework and the veneer may, for example, be ground or milled from a blank, or cast from a molten ceramic, glass or glass ceramic material.
Dental restorations are often manufactured by an automated process, which typically includes:                capturing the shape of a patient's teeth, for example by scanning a plaster model of the patient's teeth or alternatively by scanning the actual teeth in the patient's mouth;        designing the shape of a dental restoration precursor based on the captured shape using a computer-aided design (CAD) software;        machining the dental restoration precursor to correspond to the designed shape, for example, by an automated Computer Numerical Controlled (CNC) machine; and        finishing the dental restoration precursor by sintering and/or manual veneering. For example U.S. Pat. No. 6,398,554 discloses a method for producing a dental prosthesis which includes computer modeling of a three-dimensional prosthetic cap based on an human implantation zone. The method first includes casting an impression of the implantation zone of the human body. Then a digital three-dimensional representation of the implantation zone is made by sensing the implantation zone with a sensor. From this, a digital representation of the internal surface of the prosthesis is defined on the basis of the digital three-dimensional representation of the implantation zone. A digital three-dimensional representation of the external surface of the prosthesis is then defined on the basis of the surrounding parameters of the prosthesis and the digital three-dimensional representation of the internal surface of the prosthesis. Then, a digital three-dimensional representation of the external surface of the cap is defined on the basis of the external and internal surfaces of the prosthesis. Based on this three-dimensional model, an actual prosthetic cap can be produced.        
It is desirable that the dental restoration also has an appearance that matches or approximates the appearance of adjacent teeth. The appearance of natural teeth is on the one hand provided by color shades, and further by a certain translucency. A dental technician or a dental practitioner, for example, typically selects the color of the ceramic material to be used for the dental restoration according to the teeth in a patient's mouth that are located next to the tooth or teeth to be restored. For example, the appearance of relevant teeth in a patient's mouth may be determined using shade guides and the color shade for the framework and the veneer may be selected accordingly. The general types of ceramic or glass-ceramic materials for the framework and the veneer are typically selected to meet certain mechanical and aesthetic requirements for the dental restoration, one of which is the desired translucency.
Manufacturers of dental ceramic materials in particular often offer one or more certain ceramic and/or glass-ceramic materials in a variety of different color shades, and a dental technician or a dental practitioner usually selects the shade of the material that is closest to the desired shade. Many approaches have been tried to provide ceramic material in color shades that match the desired color as closely as possible.
Although the current approaches for manufacturing of dental restorations may provide a variety of advantages, there is still a desire for a method of manufacturing dental restorations in a cost efficient manner and at a good aesthetic quality.